Method of making motor fuel



Patented Mar. 27, 1951 t 1 s01 B. Wiczer, WashingtomD. o.

No Drawing. Application September-"17, 1945;

Serial No. 616,797

1 Claim.

The :presentinvention is acontinuation in part of my copending application Serial Number 436,019, filed March v24, .1942, now Patent No. 2,384,866, and relates to. a method. of treating liquid hydrocarboncontaining'substantial .qualities I. of undesirable unsaturates usually resulting from oil pyrolysis with. or without catalysts and boiling within the range from about 80 degrees to 800 degrees'F. and, thus, includes within its scope commercialcracked gasolines,. Diesel fuels and light distilled burning cr -range oils such as kerosene.

The unsaturated hydrocarbon content, as contained in crackedgasoline, or the lower boiling distillate (80 F.400 F.) as usually used as motor fuelin spark fired Otto cycle motors, represents avaluable component because of its high antiknock character. It hasthe disadvantage that it forms gums in storage and in the motors. The unsaturated content is substantial andmay range from 20-60%, dependent upon the method of cracking. Where the cracking has been conducted with catalysts the quantity of unsaturates present may be somewhat less than this indicated, however catalytically cracked. hydrocarbon will be similarlyimproved by the treatment according to the present invention.

For ordinary automobile motors, cracked gaso- 1ine.in present day practice treated bypolymerization, filtration throughcelay, or by dilute acid washing to remove .a portion of the most active gum-forming components which, incidentally, are of the most valuable anti-knock character. The remainderof the fuel is then doped with strong anti-oxidants to prevent oxidation overaperiod of a few months to allow marketing. Such fuelis not entirely gum-free and must often be used with special heavy solventstokeep the gum in suspension and remove it together withoccluded carbon from the combustion chambers. This product, therefore, represents a refinerscompromise to lose as little of the fuel as possible while-stabilizing it to a degree only satisfactory for quick use in commercial transportation.

This fuel isnot susceptible to substantial improvement .in anti-knock value :by doping with lead tetraethyl because of its unsaturated hydrocarbon content. Hence, it cannot be used in aviation motors both because it cannot be doped to the super high octane anti-knockvalue required for high compression aviation motors and because the gum-forming unsaturated constituents cannot be adequately stabilized for aviation motor requirements wherein any gum: depositiOhx cOll1d not be tolerated.

It has been the practice for aviation fuel blends to avoid use of the present great bulk fuel. supply of cracked gasoline because of its unsaturated character and to rely largely upon special synthetic isoparaffins formed fromalkylation andhydropolymerizationofthe C3-C4 fraction of the byproduct gases produced in gas oil cracking. Hence, the high anti-knock aviation-fuel supply has substantially been restricted to the-;1 or2 per cent of waste as vby-product of the normal cracked gasoline motor fuel supply. The synthetic isoparaffins must beblended with afuel base which must be'specially refined and is of poor anti-knock character and of: relatively limited supply; Such fuel base may be obtainedvfrom gasolines cracked with catalysts butonly after removal of unsaturates which represents a loss.

In the cracked higher boiling naphtha fractionsof the-kerosene type; unsaturated hydrocarbon components are undesirable for both Diesel fuel and burning oil purposes not only because of the gum-forming character'but'also because, in the-case of Diesel fuel; theihigh anti-knock unsaturates are-undesirable because-they do not burn properly in theDiesel cycle of combustion, resultingin a lower .cetane number of the fuel and in the case of burning oils, the'unsaturates burn witha smokylfiame; resulting in carbonjand soot deposition. Thus, it'is desirable to replace unsaturates in any type-ofmotorfuel or burning oil with saturated products- In its broadest aspect the present invention embracesvthe treatment of unsaturated cracked petroleum naphthas boiling in the gasoline, Diesel fuel, and burnin oil range to remove the unsaturated constituents and converting all or a substantialv portion thereof to branched chain paraffinic hydrocarbon.

The unsaturates are first extracted from cracked naphtha by treating the naphtha with an extraction' medium such as strongmineral acids, for example, -100% H2SO4, or with other known extraction solvents such as liquid sulfur dioxide, phenol, furfural, Chlorex, polyglycol ethers, etc. or mixtures thereof by conventional dual extraction processes.

In operating the present process, this extract may be acted on in its entirety as hereinafter described to convert all of the active components to branched chain paraffinichydrocarbone It is preferable, however, to first fractionate the extract to produce a low or high boiling fraction, depending upon the particular fuel for which it is intended. For example, for high anti-knock spark-fired motor fuel, the lower boiling fraction from 80 to 200 or 80 to 150 F. would be preferred in order that the product, when converted to branched chain paraffinic hydrocarbon, will boil in lower boiling range desirable for this type of fuel. It will be apparent that if the so-called safety high flash point fuel were specified, a higher boilin fraction of extract boiling from 125 to 250 F. would be used. For use in Diesel fuels and burning oils, the use of the higher boilmg fractions from 200 F. to the end point of 500 to 800 F. would be preferred.

It is further desirable to extract from any particular fraction the more readily reactable unsaturates, for example, the tertiary olefins, so that a higher yield of branched chain paraflinic hydrocarbon may be produced by more rigid control of reaction conditions upon easily reactable olefins as distinguished from the less easily reactable unsaturates, each being subjected to optimum reaction conditions for its type. Tertiary olefins are readily separated by treating the original extract or fraction thereof with 60-65% H2SO4 or a selective solvent such as phenol. In an alternative method, suitable catalysts, such as BF3, boron fluoride, in alcohol or acetic acid solution may be used which reacts selectively with only the tertiary olefins, the secondary or less reactive olefin being reacted at a later stage or discarded.

The extract or fraction according to the present invention is now alkylated with methane or ethane gas to effect substantial saturation thereof. According to this method of alkylation the extract is treated with methane and hydrogenation catalysts at low temperatures 100-600 F. and high pressures so that free methyl radicals produced as intermediates are caused to add to the extract.

Not only do the olefins otherwise wasted provide a source from which the saturated hydrocarbon may be prepared for blending with motor fuels, but the very method of obtaining the olefin by extraction from the naphtha provides a saturated blending base fuel containing no undesirable olefins, a characteristic which makes the present process of outstanding value for preparation of 100 plus aviation fuels.

It will be apparent that the aromatic content of the extract may similarly be desirably converted to the type of derivatives set forth above, but since it is a desirable fuel component particularly in gasolines, it may be separated and returned to the rafifinate without treatment.

Example A raw vapor phase cracked gasoline boiling from 80 to 400 F. was extracted with liquid sulfur dioxide according to the Edcleanu process. After removal of sulfur dioxide, the extract was fractionated to obtain a cut boiling from 80 to 175 F. Alternatively the entire extract may be treated or extracts of unsaturated petroleum fractions of higher or lower boiling ranges.

Any such olefine preferably a high volatile fraction rich in tertiary olefines is reacted in a hydrogen exchange reaction sometimes known as intermolecular hydrogenation with gaseous hydrocarbon such as methane, ethane or propane, preferably methane, by reacting the extract with an excess of methane for hydrogenation thereof in the presence of aluminum chloride at about 600 F. and high pressures 60 to 100 atmospheres. The catalyst is carried on an inert carrier such as silica, alumina or diatomaceous earth which has been treated with dry hydrogen chloride and minor quantities of activating metals such as reduced nickel or platinum. The cfiiciency and degree of alkylation depends on the time of contact, the contact being short and rapid for select fractions such as tertiary olefines, but a fraction containing aromatics takes longer. For purposes herein the extract is contacted with the catalyst at a 10 to rate and 5 to 12% for an aromatic fraction (weight of extract per weight of catalyst per hour). The saturated gas is used in preferably two or three times the molecular ratio required for saturation by alkylation but a larger excess up to 10 times may be used and the extract vapors and methane are passed under the conditions stated over the catalyst. The reaction product is separated from unreacted portions by extraction and the raffinate is reblended with the original raffinate. The extract may be fractionated and recycled to the reactor after proportions are readjusted, or it may otherwise be treated according to other unsaturated treatments herein or discarded. Where higher temperatures are used, i. e. up to 800 F., alkylation is effected in higher yield, but side reactions such as polymerication of the olefine also takes place at a higher yield tending to destroy its utility as recycle stock. Where mixtures of methane with higher alkanes such as ethane and propane are used a progressively lower temperature may be used ranging from 400 to 600 F. and if the higher molecular weight gas is used alone (propane) it is desirable to use the lower temperature or 300 to 400 F.

Having thus described my invention, I claim:

Process of treating olefines comprising passing a mixture thereof with an excess of methane over a catalyst comprising aluminum chloride and activating metals selected from the group consisting of nickel and platinum on a carrier at a temperature from 400 to 800 F. and. a pressure of to atmospheres.

SOL B. WICZER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,608,328 McAfee Nov. 23, 1926 1,608,329 McAfee Nov. 23, 1926 2,304,183 Layng et a1 Dec. 8, 1942 2,326,586 Vesterdal Aug. 10, 1943 2,379,334 Atwell June 26, 1945 2,383,056 Goldsby Aug. 21, 1945 2,384,866 Wiczer Sept. 18, 1945 2,389,176 Anderson Nov. 20, 1945 2,391,962 Goldsby Jan. 1, 1946 OTHER REFERENCES Ipaticff et al.: J. Am. Chem. Soc., vol. 57, pages 1616-4621, Sept. 1935.

Egloff et al.: Chemical Reviews, vol. 37, pages 323-399 (only pages 395-6 necessary).

Thomas: Anhydrous Aluminum Chloride in Organic Chemistry, copyright 1941 by Reinhold Publishing Corp., 330 W. 42nd Street, New York, N. Y., page 738. 

